Cone of silence simulator



May 14, 1957 c..1. KENNEDY n 2,791,842

i coNE oF SILENCE: sIlvlULATQR4 Filed April 2. 19532 2 Sheets-Sheet 1 vvvvv 400 Cral POM/fk l JUPPL y A A l." 00Min/Tfn A7 ran/v1.17

CoM/'u TIR 2,791,842 com; or SILENCE sIMULAron Charles J. Kennedy, Sun Valley, Calif., assigner to yCollins la'dio Company, Cedar Rapids, Iowa, a corporation of owa Application April 2, 1952, Serial No. 280,089

1 Claim. .(Clr. 35.11102) This invention relates to means for simulating a radio range in the vicinity of the station.

It is oftentimes desirable to train ilight crews on the ground where their errors will not prove fatal and Where the4 expense is much less than inthe air. For example, the co-pending application entitled Synthetic A/N Range, Pa-tent Number 2,621,425, issued December 16, 1952, assigned to Collins Radio Company, discloses an A/N range simulator for a student.

That invention disclosed means for setting an A/N range station soV that the student can orient himself with respect to the station. The present invention is a supplement to that one and relates to means for a build-up in the immediate vicinity of thestationfand a cone of Silence over the station. Actual radio installations of A/N range stations have the characteristic that as the plane approaches the station, the signal builds up rapidly to a peak and then falls 'to a dead silence in a zone immediately above the station. This indicates to the pilot when he is directly over the station.

lt is an object of this invention, therefore, to provide a synthetic build-up and cone of silence device for a synthetic A/N range station.

Further objects, features and advantages of this invention will become apparent from the following description and claims when read in View of the drawings, in which: Figure 1 illustrates a portion of the circuitry of this invention;

Figure 2 illustrates a second portion of the circuitry;

Figure 3 is a graphic representation showing the aircrafts position with respect to the station; and

Figure 4 illustrates the gradual fade circuit of this invention.

With reference to Figure 3, let it be assumed that an aircraft P is located a distance R from a station S and that with respect to Cartesian coordinates the point P may be located with respect to the station S by AY and AX.

Figure l illustrates a AX computer which continuously computes the distance AX. A AY computer 11 continously computes the AY component. Such computers are well known to those skilled in the art but for illustration, the values of AX land AY may be set in manually by the instructor. The outputs of the AX and AY computer are furnished to ampliers V1 and V2, respectively, through resistors R1 and R2.

The outputs of amplifier V1 and V2 are passed to second amplifiers V3 and V4 to obtain high level amplitication. A battery E1 is connected to the plates of the four amplifier tubes to supply the plate voltage.

A 400 cycle power supply 13 supplies an input to the primary 14 of a transformer which has a pair of secondaries 16 and 17 that each have their ends connected to the mid-point of secondaries of transformers 18 and 19.

The primary 21 of transformer 18 is connected to the plate of the tube V3 and the primary 22 of transformer 19 is connected to the plate of tube V4.

A pair of phase detectors are designated generally as United States Patent Patented -May 14, 1957 23 and 24, respectively, and each comprise a pair of diodes V5, Vs, V1 and Ve, which have their plates connected toopposite ends of the secondaries of the ltransformers 13 and 1.9. One end of the secondary 1 6 is connectedbetween a pair of condensersCi and C2 which are connected between the cathodes of tubes V5 and Va, One end of the secondary'l? is connected between condensers C3 and C4 which are connected between the cathodes of tubes V7 and Vs.

Polarity reversing circuits 26 and 27 are connected to each phase detector 23 and 24 and each comprise four diode rectiiiers which might beg'for example,V selenium diodes with two of the diodes connected in series with the phase detector outputs and two in parallel in an X fashion as shown. The outputs of the polarity reversing circuits 26 and 27 are connected together so that the largest signal will predominate. The loutput is connected to terminal 28.

Figure 2 shows the terminal 28 which is connected to a circuit comprising diodesl 29 and 31 which have condensers Cs and Cfr connected` across them.

An audio signal generator 32 supplies an input to a pentode V9 which has the circuit comprising the diodes 29 and 3.1 connected between its control gri-d and cathode. The circuit comprising the diodes 29 and 31 vand condensers-Cs and C7 has the characteristic that .when the direct current input from the polarity reversing'c'ircuits 26 and 27' goes to ,zero the impedance of thecircuit is very high, but when the direct current signal supplied to terminal 28 is positive, the impedance of the circuit is very low.

A gradual fade circuit 33 is also connected to the control grid 35 of variable mu pentode V9 to vary its output in inverse proportion to the distance from the station. The gradual fade circuit 33 is shown in detail in Figure 4. It comprises a battery Ez Whichhas its positive terminal connected =to ground and its negative terminal connected to a resistor Ra. The other sideof resistor Ra is connected to ground. A slide contact 41 engages resistor Re. and is controlled by a shaft 42 which has a knob 43 attached thereto. The contact 41 is connected to the output conductor of the gradual fade circuit 33. The knob 43 may be controlled manually by the instructor to simulate an approach to the radio station. It is to be particularly noted that the output of the gradual fade circuit becomes more positive as the distance to station becomes smaller.

The plate of the pentode V9 is connected to a transformer 34 which has the mid-point of its secondary connected to the terminal 28. A ring modulator circuit 36 is connected across the ends of the secondary. The ring modulator 36 is connected to the primary of a transformer 37 which has its secondary 38 connected to earphones 39 and 40. The earphones furnish the audible signal to the student.

The ring modulator circuit has the property of being balanced and hence transmits no signal from transformer 34 to transformer 36 when the voltage applied to terminal 28 is zero. When voltage is applied to terminal 28 as is the case when the aircraft is other than directly over the station, the ring modulator passes a signal proportional to this D. C. voltage. When the voltage at terminal 28 has reached a value of about .l0 volt, further increases no longer bring about proportionate increases in audio signal level since the ring modulator reaches saturation. The D. C. voltage reaches this saturation level only a short distance from the station owing to high amplification in the AX and AY amplifiers.

It may be seen from the explanation above that the signal from the ring modulator circuit will be zero directly over the station and will increase sharply as the aircraft progresses away from the station until it reaches effective resistance when the voltage applied to terminal 28 is zero, is utilized to provide variable attenuation such that when the output voltage of bridge rectiers 26 and i 27 drops as the station is approached, the audio signal level applied to transformer 34 through ampliiier V9 is rapidly increased. It is this increased signal which is attenuated by the ring modulator when its action commences still closer to the station.

Thus, it may be seen that the sequence of events is as follows: Starting from a point distant from the station,v

as the aircraft proceeds, less negative voltage is applied to variable mu amplier V9 causing its output to increase slowly as a radio signal would in an aircraft receiver having no AVC action. At a point close to the station, the amplilier outputs begin to drop as does the D. C. signal derived from those outputs. At a distance corresponding to approximately .5 volts D. C. on terminal 28, the resistance of diodes 29 and 31 begins to increase causing the audio signal to rise.

This rise continues until the voltage at terminal 28 drops to a level of .10 volt whereupon the ring modulator is no longer saturated and it begins to attenuate the audio signal. Attenuation increases as the voltage on terminal 28 drops until, at zero D. C. volts, almost no audio signal passes through the ring modulator circuit. As the air- 3()v craft passes over the station the reverse of the above action takes place with the ring again becoming unbalanced and passing signal up to the point of saturation and the r ring modulator.

diodes circuit taking over and dropping the audio signal down to the distant level.

Although this invention has been described with respect to particular embodiments thereof, it is not to be so limited as changes and modifications may be made therein which are within the full intended scope of the invention, as dened by the appended claim.

I claim:

Means for simulating a radio range station in the vicinity of a cone of silenceV comprising, an audio signal generator, an electron tube receiving an output from said audio signal generator, a pair of computing means producing outputs corresponding, respectively, to the Cartesian coordinates of the simulated position relative to the station, a pair of phase detectors connected respectively to the 'outputs of the computing means, a pair of polarity reversing circuits connected to the outputs of the phase detectors so as to always produce one polarity, the outputs of the two polarity reversing circuits connected together so that the larger one dominates, a variable attenuating circuit connected to the control grid fof said electron tube, the outputs of said polarity reversing circuits connected to said variable attenuating circuit, a ring modulator coupled to the output of said electron tube, and audible signal reproducing means coupled to the References Cited in the file of this patent UNITED STATES PATENTS 2,429,597 Andrews Oct. 28, 1947 2,510,384 Dehmel June 6, 1950 2,514,602. Grandmont July 11. 1950 

